Physicochemical Stability of Extemporaneously Prepared Methylcobalamin Injections in the Presence and Absence of Preservative and the Impact of Light Exposure.

Methylcobalamin, one of the two active forms of vitamin B12, is the most effective analog in permeation and in transportation of neurons in subcellular organelles. Formulations of methylcobalamin are only commercially available in a few countries, which make them inaccessible for most patients. Extemporaneously prepared injections become the only option for those patients. The objective of this work is to study the physical and chemical (ultrahigh- performance liquid chromatography stability-indicating method) stabilities of methylcobalamin injections in the presence and absence of preservative during 181 days (considering the stability limit as 90% of initial concentration of methylcobalamin). The light exposure stability of injections in amber serum vials or clear syringes, solution in amber or clear glassware under typical pharmacy, clinical, and laboratory settings are also presented. Methylcobalamin injections, regardless of the concentrations and inactive ingredients, remained stable for at least 181 days at room temperature when stored in amber serum vials and protected from light. These experimental data suggested that the methylcobalamin injection solutions should be protected from light completely and light exposure in pharmacy, clinical, and laboratory setting should be minimized.